488 CHAPTER 9 Inferences from Two Samples 10. Second-Hand Smoke Samples from Data Set 15 “Passive and Active Smoke” include cotinine levels measured in a group of smokers (n = 40, x = 172.48 ng>mL, s = 119.50 ng>mL) and a group of nonsmokers not exposed to tobacco smoke (n = 40, x = 16.35 ng>mL, s = 62.53 ng>mL). Cotinine is a metabolite of nicotine, meaning that when nicotine is absorbed by the body, cotinine is produced. a. Use a 0.05 significance level to test the claim that the variation of cotinine in smokers is greater than the variation of cotinine in nonsmokers not exposed to tobacco smoke. b. The 40 cotinine measurements from the nonsmoking group consist of these values (all in ng>mL): 1, 1, 90, 244, 309, and 35 other values that are all 0. Does this sample appear to be from a normally distributed population? If not, how are the results from part (a) affected? 11. Bicycle Commuting A researcher used two different bicycles to commute to work. One bicycle was carbon and weighed 20.9 lb; the other bicycle was steel and weighed 30.0 lb. The commuting times (minutes) were recorded with the results shown below (based on data from “Bicycle Weights and Commuting Time,” by Jeremy Groves, British Medical Journal). Use a 0.05 significance level to test the claim that commuting times with the lighter bicycle have more variation than commuting times with the heavier bicycle. Lighter Bicycle: n = 26, x = 108.4 min, s = 6.3 min Heavier Bicycle: n = 30, x = 107.8 min, s = 4.9 min 12. Birth Weights Listed below are birth weight statistics from Data Set 6 “Births” in Appendix B. Use a 0.05 significance level to test the claim that at birth, weights of girls have more variation than weights of boys. Girls: n = 205, x = 3037.1 g, s = 706.3 g Boys: n = 195, x = 3272.8 g, s = 660.2 g 13. Female and Male Pulse Rates Listed below are pulse rates of randomly selected subjects from Data Set 1 “Body Data.” Use a 0.05 significance level to test the claim that the variation among pulse rates of females is greater than the variation among males. Female 56 54 72 70 80 72 62 96 72 60 98 72 Male 76 78 78 84 74 72 60 70 66 14. Weights of Female Army Personnel Listed below are weights (kg) of randomly selected female U.S. Army personnel from Data Set 2 “ANSUR I 1988” and Data Set 3 “ANSUR II 2012.” Use a 0.05 significance level to test the claim that the variation among weights did not change from the ANSUR I study in 1988 to the ANSUR II study in 2012. ANSUR I 1988: 70.1 65.6 62.2 59.6 57.3 67.7 59.2 57.3 57.0 66.2 68.4 51.5 ANSUR II 2012: 71.2 72.2 61.0 81.7 79.9 60.2 58.4 60.1 83.4 97.3 15. IQ and Lead Exposure Data Set 11 “IQ and Lead” in Appendix B lists full IQ scores for a random sample of subjects with medium lead levels in their blood and another random sample of subjects with high lead levels in their blood. Those IQ scores are listed below. Use a 0.05 significance level to test the claim that IQ scores of subjects with medium lead levels vary more than IQ scores of subjects with high lead levels. Medium: 72 90 92 71 86 79 83 114 100 93 91 98 91 46 85 82 97 91 92 77 111 78 High: 82 93 85 75 85 80 101 89 80 94 88 104 88 88 83 104 96 76 80 79 75
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